<template>
  <div>
    <router-link tag="div"
                 to="/"
                 v-show="showAbs"
                 class="header-abs">
      <div class="iconfont header-abs-back">&#xe743;</div>
    </router-link>
    <div class="header-fixed"
         v-show="!showAbs"
         :style="opacityStyle">
      景点详情
      <router-link to='/'>
        <div class="iconfont header-fixed-back">&#xe743;</div>
      </router-link>
    </div>
  </div>
</template>
<script>
export default {
  name: 'DetailHeader',
  data() {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  created() {
    window.addEventListener('scroll', this.handleScroll)
  },
  beforeDestroy() {
    window.removeEventListener('scroll', this.handleScroll)
  },
  methods: {
    handleScroll() {
      const top =
        document.documentElement.scrollTop ||
        document.body.scrollTop ||
        window.pageYOffset
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = {
          opacity
        }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  }
}
</script>
<style scoped lang='stylus'>
@import '~@/assets/styles/variables.styl'
.header-abs
  position: absolute
  left: .2rem
  top: .2rem
  width: .8rem
  height: .8rem
  border-radius: .4rem
  text-align: center
  line-height: .4rem
  background: rgba(0,0,0,0.8)
  .header-abs-back
    color: #fff
    font-size: .5rem
    height: .8rem
    line-height: .8rem
.header-fixed
  position: fixed
  z-index: 2
  top: 0
  left: 0
  right: 0
  height: $headerHeight;
  line-height: $headerHeight;
  color: #fff;
  hidden: hidden;
  text-align: center;
  background-color: $bgColor;
  font-size: 0.32rem;
  .header-fixed-back
    position: absolute
    width: 0.64rem
    font-size: .4rem
    text-align: center
    top: 0
    left:0
    color: #fff
</style>
